Tap



Patented May 9, 1933 UNITED STATES P ENT. oFFi'ca JESSE n. TUCKER, OF NORTH SACRAMENTO, CALIFORNIA, ASSIGNOR TO TUCKER- G-ILMORE MFG. COMPANY, OF NORTH SACRAMENTO,

OF CALIFORNIA CALIFORNIA, A CORPORATION TAP:

Application filed November 11, 1930. Serial No. 494,889.

This invention relates to machine taps such as are used for forming threads inthe holes of metal parts. Such taps as they are now constructed are inclined to bind in the holes and consequently are very easily chipped or broken. This is especially the case in the smaller sizes of tap. Also owing to the construction of the tapsthere is a tendency for the metal chips or shavings as they are formed to be broken up into small particles rather than being allowed to escape freely from the hole, and these particles find their way into the thread grooves being formed and obstruct the efficient action of the tap.

The principal objects of my invention are to provide a tap of this character in whlch the above objectionable and defective features are eliminated, since the tap is so constructed that great strength is had, breakage is practically eliminated, the metal chips or shavings have greater freedom of exit, and there is no binding or possible deflection of the tap from its central position in the hole.

A further object of the invention is to produce a simple and inexpensive device and yet one which will be exceedingly effective for the purpose for which it is designed.

These objects I accomplish by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claim.

In the drawing similar characters of reference indicate corresponding parts in the several views:

Fig. 1 is alongitudinal elevation of my improved tap, looking at one side of the same.

Fig. 2 is a similar view looking at the opposite side.

Fig. 3 is a cross section on the line 33 of Fig. 2.

Fig. 4 is a cross section of a modified form of tap.

Referring now more particularly to the characters of reference on the drawing, the tap comprises a body 1 having an end shank 2 adapted for non-turning engagement with a chuck or the like as usual. The body is threaded as at 3 from its end opposite the shank and for the greater portion of its length; the threads being continuous about the body for an extent somewhat greater than i one-half its circumference, or 180 degrees. The" threads are flattened as they approach the outer endof the body, as is customary,so that the tool is tapered at that end. Between the separated ends of the segmentalthread portions thebody is provided with an integral rib 4. which extends lengthwise of the bodyand whose outer surface is inset from thecircuniferential plane of the outer edges of the threads. Between the leading end of the threads and the adjacent side of the rib, a relatively deep and wide and round bottomed'recess or flute 5 is formed forthe full lengthof said rib and threads; while between the opposite end of the threads andthe rib a similar but shallower and narrower flute 6 is formed. Foradistance of lessthan 90 degrees about the body the threads from their leading end are relieved or depressed for their full depth relative to the normal thread or bore circle shown at 7. V V The rib 4 tapers in cross section from'its outer end to its junction with the shank, the edge of the rib alon the flute 6 being parallel with the line of thebody' along said flute while the edge along the flute '5' inclines toward the line of the body along such flute 5 in the direction ofthe shank.

, The large flute 5 when the tap is inserted in a'hole and rotated, is engaging the'chips or shavings as cut from the metal and provides for'the easy exit of the same from the hole, without: the shavings breaking up 'intorelatively small pieces and becoming jammed in the thread groovesas formed, as is the case the rib 4 and body 2 along this flute 5 forces the shavings progressively toward the outlet at the shank. The threads being relieved for a certain distance from their leading end, they are presented to the bore in such a manner as to out easily into the metal without any binding effect being had such as places a heavy strain on the tap. The danger of breakage is therefore greatly lessened if not entirely eliminated. The threaded portion of the tap being continuous for more than 180 degrees about the body, said body is pre vented from deflecting from a true central with ordinarytaps. Theconverging sides of Iposition in the bore, and the threads bear rmly against the bore at a point diametrally opposed to the leading end of the threads, thus further preventing any tendency for the tap to bend or be deflected from place. The turning of the tap into the metal also places a strain thereon at the leading ends of the threads tending to deflect the tap laterally in a'direction opposite to the direction of rotation; "This is prevented by the engagement of the threads just beyond their relieved portions with the metal about the hole. The flute 6 permits of the ready escape of any chips which may be present or formed when the tool is being backedaway. The rib 4 of course imparts strength to the body without interfering with the cutting action or with the passage of the chips or shavings from the hole, and is especially necessary in the smaller taps. In the large sizes however, this rib can be eliminated, and the body 1a may be made so as to be substantially D shaped in cross-section, as shown in Fig. 4.

From the foregoing description it will be readily seen that I have produced sucli a device as substantially fulfills the objects of the invention as set forth herein. 7

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail maybe resorted to as do not form a departure fromthe spirit of the invention, as defined by the appended claim.

Having thus describedmy invention what Iclaim as new and useful and desire to'secure by Letters Patent is: i i

,Atap comprising a body, and threadsextending continuously about the body for i more than 180 of the circumference thereof, saidbody being cut away lengthwise at the endsof saidcircumferential portion to provide abrupt terminations of the threads; said threads being depressed between their leading terminations and a point about the thread circle a distance less than 90 from said leading terminations while the remainder of the V threads including the leading terminations lie in a common circle concentric with. the axis ofthc tap} v 'f In testimony whereof I affix my signature. JESSE D. TUCKER. 

